12.307 Weather and Climate Laboratory

How to Compute Thermal Wind from Climatological Data Using MATLAB

First, open the National Centers for Environmental Prediction (NCEP) Reanalysis plotting interface.

1. Plot and download temperature data for one pressure level.
(a) On the plotting interface page, scroll down and select 'Air Temperature' and click 'Search.'

(b) On the new page, scroll down and click the 'Make plot or subset' link in the row corresponding to the second appearance of 'monthly long term mean.'

(c) On the new page, type '0' for begin lat to acquire only Northern Hemisphere data.  Next, select a pressure level and a winter month to compute the climatological average field.  An example (shown on right) could be to choose the 500 mb surface for January.  Then, plot the temperature data to determine where to take your polar front cross-section.  Select 'plot on a white background,' click the 'polar stereographic' box, set the 'scale plot' to 150%, and finally click 'Create plot or subset of data.'

(d) From your plot, identify a longitude of strong temperature gradient (along with the latitudinal range of this gradient).  Select the link 'FTP the data,' appearing below your plot, and save the file.  
(e) Use the MATLAB script to plot the data for your identified longitude and latitudinal range.  
2. Plot and download zonal wind data for two pressure levels.
(a) On the plotting interface page, scroll down and select 'U-wind' and click 'Search.'
(b) On the new page, scroll down and click the 'Make plot or subset' link in the row corresponding to the first appearance of 'monthly long term mean.'

(c) On the new page, type '0' for begin lat to acquire only Northern Hemisphere data.  Next, select a pressure level and a winter month to compute the climatological average field.  An example (shown on right) could be to choose the 400 mb surface for January.  Then, plot the wind to confirm that your cross-section identified using the temperature data corresponds to a region of strong zonal wind.  Select 'plot on a white background,' click the 'polar stereographic' box, set the 'scale plot' to 150%, and finally click 'Create plot or subset of data.'

(d) Once you have confirmed that your cross-section region has strong zonal winds, scroll down and select the link 'FTP the data,' and save the file.  
(e) Repeat the download procedure for another pressure level, e.g. 600 mb.  
(f) Use the MATLAB script to plot the data for your identified longitude and latitudinal range.  


 



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Last updated: March 10, 2009.